Control device for controlling discharge of settlings from a water scalping tank or the like



April 21, 1964 c. B. COCHRAN 3,129,849

CONTROL DEVICE FOR CONTROLLING DISCHARGE OF SETTLINGS FROM A WATER SCALFING TANK OR THE LIKE Filed March 16, 1962 2 Sheets-Sheet 1 Invefz'tor I Clement 3. Co c bran.

Ba. andfim ornggs Apnl 21, 1964 c. B. COCHRAN 3,129,849

CONTROL DEVICE FOR CONTROLLING DISCHARGE OF SETTLINGS FROM A WATER SCALPING TANK OR THE LIKE Filed March 16,- 1962 2 Sheets-Sheet 2 41 I 52 4 Inventor 3e .i, I i m 55 Clement B. Cochran Er": =1'\ 53, 215421, Ka n-3w Mam ornegds United States Patent CONTROL DEVICE FOR CONTROLLING DIS- CHARGE OF SETTLINGS FROM A WATER SCALPING TANK OR THE LIKE Clement B. Cochran, Des Moines, Iowa, assignor to Eagle Iron Works, Des Moines, Iowa, a corporation of Iowa Filed Mar. 16, 1962, Ser. No. 180,302 7 Claims. (Cl. 222-64) This invention relates to a new and improved sensing and control device and more particularly to a new and improved control device for actuating a discharge valve in a water scalping tank or similar apparatus in which solid or semi-solid material is settled out of a fluid medium.

A typical water scalping tank, utilized for the classification of sand or other insoluble granular material initially suspended in a fluid medium, usually Water, comprises an elongated tank into which a slurry of the sand or other material is introduced. The mixture of granular material and water flows into one end of the tank with excess fluid overflowing the opposite end. The sand settles to the bottom of the tank, the larger particles settling near the input end with progressively finer particles settling toward the overflow end of the tank. Sand outlets are located at spaced intervals along the bottom of the tank and are employed to discharge the various sizes of sand as they accumulate at the bottom of the tank. By controlling the operation of discharge valves at the outlets, the gradation of sand can be controlled to meet predetermined specifications.

In order to avoid excess discharge of fluid from the scalping tank, and to obtain reasonable accuracy in the constituency of the discharged material, it is necessary to maintain the discharge valves closed except when a predetermined level of sand has accumulated over each valve. Consequently, it is necessary to provide some means for sensing the level of accumulated sand at each discharge station. One known sensing device that has proven satisfactory in many applications comprises a paddie or like rotary member, mounted on a shaft that projects downwardly into the settling tank to a predetermined level above the discharge valve. A drive motor or like means is provided for rotating the paddle, the applied torque being suflicient to maintain the paddle in continuous rotation as long as it is immersed in a substantially fluid medium. When solid material accumulates to the level of the paddle, however, shaft rotation is interrupted arid the drive motor stator rotates through a limited arc. Rotation of the drive motor stator actuates a control switch that opens the valve with which the paddle is associated. When the discharge through the valve lowers the accumulated solid material to an extent sufficient to free the paddle, restoring springs are employed to return the sensing paddle drive motor stator to its original position and rotation is resumed.

Accurate sensing is sometimes difficult to achieve, using a sensing device of the aforementioned kind, particularly at that end of the tank at which fine sand or other granular material accumulates. It is ditficult to calibrate the restoring springs; if the springs are too strong they tend to prevent initial actuation of the sensing device and to allow excessive accumulation of the material, and if the springs are too weak the sensing device may be unable to maintain continuous rotation due to the drag produced by the fluid medium in which the paddle operates. Thus, the conventional devices do not afford the relatively high sensitivity necessary for efiective and accurate operation at the fine end of the water scalping tank where tightly controlled specifications must be observed with respect to the sand discharge.

3,129,849 Patented Apr. 21, 1964;

It is a principal object of the invention, therefore, to provide a new and improved sensing and control device, for a water scalping tank or like apparatus in which material is settled out of a fluid medium, that afi'ords substantially improved sensitivity as compared with previously known sensing apparatus.

Another object of the invention is to provide auto matic self-restoration in a sensing and control device for a water scalping tank or the like that does not entail restoring springs or similar mechanisms. A related object of the invention is to utilize the actual discharge of material, through an outlet valve in a water scalping tank or the like, to effect restoration of the discharge valve to an initial closed condition.

Another object of the invention is to provide for a relatively high frequency of operation, with respect to a discharge valve in a water scalping tank or like apparatus, by utilizing a sensing and control device that does not require springs or other inertia mechanisms for restoration, thereby affording a more even distribution of material discharged from the valve.

A particular object of the invention is to provide a sensing and control device, for a discharge valve in a water scalping tank or like apparatus, that automatically recloses the valve in response to a discharge of material through the valve, yet which also operates to keep the valve closed in the absence of a substantial accumulation of settled material.

Thus, the present invention relates to a sensing and control device for a discharge valve in a water scalping tank or like apparatus in which material is settled out of a fluid medium. In accordance with the present invention, the device comprises a sensing rotor shaft that extends into the fluid in the tank and drive means for rotating the shaft in a given direction. Sensing rotor means are mounted on the shaft at a predetermined level relative to the discharge valve, and this sensing rotor means is effective to apply a reaction torque to the shaft, in opposition to the drive torque from the drive means, that is suflicient to interrupt rotation of shaft whenever settled material exceeds the level of the rotor means. The sensing rotor means also includes means for applying a restoring torque to the shaft, in aiding relation to the torque from the drive means, directly in response to an outward discharge through the valve. The latter means may be provided by adopting a specific configuration for the sensing rotor, or may constitute a separate element of the sensing rotor means. In addition, the device includes control means for sensing interruption in rotation of the shaft and for actuating the discharge valve in response thereto.

Other and further objects of the present invention will be apparent from the following description and claims and are illustrated in the accompanying drawings which, by way of illustration, show a preferred embodiment of the present invention and the principles thereof and what is now considered to be the best mode contemplated for applying these principles. Other embodiments of the invention embodying the same or equivalent principles may be used and structural changes may be made as desired by those skilled in the art without departing from the present invention and the purview of the appended claims.

In the drawings:

FIG. 1 is a longitudinal sectional elevation View of a water scalping tank that utilizes a plurality of sensing and control devices constructed in accordance with the present invention;

FIGURE 2 is a sectional elevation view of a part of the water scalping tank of FIG. 1, taken approximately along line 22 therein, but drawn to a larger scale than FIG. 1;

FIG. 3 is a partial plan view of the sensing and control device illustrated in FIG. 2; and

FIG. 4 is a detail elevation View, partly in cross section, taken approximately as indicated at. line 4-'4 in FIG: 2.

FIG..1 illustrates a water scalping tank 10 in which sensing and control devices constructed in accordance with the present invention are incorporated. The scalping tank 10 includes a'basic tank structure comprising an input or coarse sand section 1 1 and an output or fine sand section 12, these two tank sections being joined together to afford a complete tank structure. A feed box 13, is' located at the left-hand or input end of the tank 10, an input conduit 14 being connected to the feed box. Feed box'13 has an outlet opening 15 that affords access to the interior of input tank section 11. In addition, an auxiliary water inlet 16 is located near the bottom of tank section 11 below feed box 13.

.There are six outlet or discharge stations in the scalping tank 10, the individual discharge stations being generally identified .by. the reference numerals 21 through '26. Discharge station 21 is located immediately adjacent the inlet end of tank 13' and discharge station 26 is located at the opposite or right-hand end of the tank. Anoverfiow conduit 28 is located at the right-hand end of tank 10, and this conduit receives the excess of fluid flowing from the tank.

.Thedischarge stations 21 through 26 are provided with individual discharge valves which are identified as valves 31 through 36. Each discharge station also includes a sensing and control device'for actuating the valve at the station. Thus, discharge station 21 includes a sensing and control device 41 of the conventional rotary-paddle kind described generally hereinabove, device 41 being utilized to control discharge valve 31. Similar sensing and control devices 42 and 43, which may also be of conventional construction, are employed to actuate discharge valves 32 and 33 respectively. Valve 34 at discharge station 24, on the other hand, is provided with a sensing and control device 44, constructed in accordance with the present invention, that is somewhat similar to the conventional paddle devices 41 43, in external appearance, but that operates in a substantially different manner. Discharge stations 25 and 26 are also provided withindividual sensing and control devices constructed in accordance with the present invention, these devices being identified by the reference numerals 45 and 46 respectively. The construction and operation of device 46, which is typical of devices 44-46, is described in detail hereinafter in connection with FIGS. 2-4.

Operation of scalping tank is initiated by feeding a slurry of sand and water into feed box 13 through conduit14, the slurry flowing from the feed box through the opening into the scalping tank. At the same time, an auxiliary flow of water may be supplied to the tank through. conduit 16. As the mixture flows from access opening'lS, the heavier particles tend to settle almost immediately, accumulating adjacent the outlet stationZl. Progressively finer particles are settled in the areas adjacent the remaining outlet'stations 22 through 26. The rate of input of the sand mixture and the water may be adjusted, usually by adjusting the water input through conduit 16, so that virtually all of the sand settles by the time the water reaches the right-hand end 12 of the scalpingtank. Thus, the overflow of water into conduit 28 is relatively clear and free of sand.

Eventually,.with continued settling of large particles from the slurry flowing into the scalping tank, the sand builds up adjacent discharge station 2-1 to a level where it interferes with operation of the sensing rotor 41. When this occurs, the resultant interruption in rotational movement' of the rotor is utilized to actuate a control switch, opening discharge valve 31. With valve 31 open, sand is discharged into the flume 37 below valve 31, reducing the level of sand accumulated in the area adjacent the discharge valve. The reduction in level of accumulated sand frees paddle 41 for continued rotation. As soon as the paddle is able to rotate. freely, a spring mechanism (not shown) is utilized to restore the control for valve 31 to its original condition, again closing the valve. This process continues during operation of the scalping tank and is described in greater detail in the co-pending application of C. B. Cochran, Serial No. 140,914, filed September 26, 1961, which describes the construction and operation of the sensing and control mechanism and also discloses a preferred control system therefor. The same cyclic mode of operation occurs at stations 22 and 23.

FIGS. 2-4 illustrate the construction of the discharge station 26, including the sensing and control device 46 that is constructed in accordance with the present invention. As shown in PEG. 2, valve 36 at discharge station '26 comprises a valve seat and guide member 51 that is fixedly mounted on the bottom 50 of scalping tank 10. .Member 51 is provided with a re-entrant flange portion 52 that affords the actual valve seat. Flange 52encompasses a relatively large central opening 53. The opening is closed by a valve disc 54 having a seal memberSS mounted upon the upper surface thereof in position to engage fiangef52. Valve disc 54 is mounted upon a valve rod 56, the valve rod extending through the valve disc and being held in place by suitable nuts or like retainers. A protective sleeve (not shown) may be mounted on the lower portion of valve rod 56, immediately above v al-ve disc 54 to protect the rod against abrasion trom sand 57 acciunrutlated in the bottom of tank 10.

The upper end of valve rod 56 is threaded into a collar' 58 that comprises the lower end of a yoke 59. A suitable lock nut 69 may be utilized to maintain rod 56 in fixedposition in collar 58 .once'adjustment of the effective length of the rod has ben achieved. The upper end of yoke 59 is pivotally connected to a piston rod 61 that projects downwardly from an operating cylinder 62. "Cylinder 62 may comprise a pneumatic or hydraulic device; if desired, a mechanical valve operator mechanism may be utilized in place of the cylinder. In the preferred arrangement illustrated in FIG. 2, however, valveactuation is accomplished by the hydraulic cylinder 62 which in turn is controlled by a solenoid operated hydraulic control valve 63.

The sensing and control device 46 comprises a sensing rotor shaft 71 that projects downwardly into the fluid in the scalping tank .10. The upper end of shaft 71 is connected by a coupling 72 to the shaft 74 of a drive motor 73. Thestator 75 of motor 73 is mounted in a supporting frame 76. The frame 76, in turn, is suspended by a swivel 77 from a fixed support 78. The swivel 77 permits axial rotation-of motor stator 75, relative to the fixed support 78, as described more fully hereinafter. The necessary electrical connections to the motor are provided by a pairof conductors 79 and 81.

Another fixed support member 82 is located immediately in front of motor 73 (FIGS. 2 and 4). A short shaft 83 is mounted upon a support member 82, as best shown in FIG. 4, and a control switch 84 is pivotally mounted upon the shaft 83. Switch 84 is a mercury switch of the kind which, when held in horizontal alignment, .is in open condition but which may be closed by tilting the switch in a given direction from the horizontal. Switch 84 is. carriedv in a mounting bracket 85 that-is journalled on shaft 83. Mounting bracket 85 includes an upwardly projecting lever 86 that extends through an aperture 87 in a forwardly projecting member 88 that comprises a part of the motor support frame 76 (FIGS. 3 and 4). Lever 86 affords a connection between control switch 84 and drive motor 73 and makes it possible to control operation of the discharge valve at discharge station'26 in response to changes in operating conditions of the motor and its output shaft, as described more fully hereinafter.

A limit member 89 of arcuate configuration is mounted on motor support frame 76 at the end of the frame opposite the connection to lever 86. As shown in FIG. 3, limit member 89 is provided at its ends with a pair of stop elements 91 and 92 which project from the limit member in position to engage the sides of support member 78 upon rotation of motor 73 and its supporting frame. Thus, stop members 91 and 92 may be utilized to define a limited range of rotational movement for the drive motor.

Control switch 84 is connected by suitable electrical conductors 93 to a terminal box 95 that is mounted upon a fixed support member 96. Terminal box 95, in turn, is electrically connected to the operating solenoid of control valve 63, the electrical connections in this instance not being illustrated in the drawings.

The upper portion of sensing shaft 71 is encased in a protective guard member 97 that is mounted on the upper or cover member 98 of scalping tank 19. At the lower end of shaft 71, a sensing rotor 101 is mounted on the shaft for rotation therewith. The mounting means for rotor v191 may be relatively simple and may comprise, for example, a cotter key 1112 that extends through the rotor and through the shaft. Sensing rotor 101 is provided with a pair of helical propeller blades 153 and 104. The blades 103 and 194 are substantially different from the conventional paddle structures used in sensing devices 41-43 (see FIG. 1) and this difference is utilized to achieve a substantially different mode of operation in sensing device 46 as compared with the known sensing apparatus.

In considering operation of sensing device 46, it may initially be assumed that the sensing device is in the operating position illustrated in solid lines in FIGS. 2-4. With scalping tank 19 in operation, fine sand or other granular material 57 begins to accumulate immediately above discharge valve 36. At first, of course, the sand does not extend up to the level of sensing rotor 191. In FIG. 2, accumulated sand 57 is shown at the level just before the sand reaches the sensing rotor.

With the scalping tank in operation, motor '73 is energized through a suitable circuit connected to leads 79 and 81. The motor remains energized continuously during operation of the scalping tank, where such operation is to be controlled by sensing and control device 46. Drive motor 73 rotates shaft 71 in the direction indicated by arrow A in FIG. 2, this being a counterclockwise direction of rotation in the plan view of FIG. 3. Motor 73 applies a predetermined drive torque to shaft 71 which is suflicient to maintain the shaft in rotation within the water or other fluid 106 with which the tank is filled.

With continuing accumulation of sand 57, the level of sand comes up above the sensing rotor. When the rotor is substantially encompassed by accumulated sand, the resultant increased drag on sensing rotor 101 produces a reaction torque, on drive shaft 71, sufiicient to interrupt rotational movement of the shaft. Motor 73, however, continues to attempt to rotate shaft 71, with the result that the motor stator 75 is rotated in a direction opposite arrow A. That is, when the sand reaches a level sufiicient to stop rotation of sensing rotor 101, the continued drive of motor 73 causes its stator to rotate in a clockwise direction as seen in FIG. 3, moving the motor support frame 76 to the alternate position shown in dash outline. The rotational movement of motor stator 75 is limited by engagement of stop element 92 of the motor support frame with the fixed support member 7 8.

Movement of the motor support frame element 88 to its alternate position 88A pulls connecting lever 86 to the left, as seen in FIGS. 2 and 3, the alternate position of the connecting lever being indicated by the dash outline 86A in FIG. 2. Movement of lever 86 to its alternate position 86A causes switch 84 to pivot in a counterclockwise direction about shaft 83 (FIG. 2), closing the control switch. It is thus seen that control switch 84, lever 86, and the connection between lever 86 and motor frame member 88 provide a control means for efiectively sensing interruption in rotation of the sensing rotor shaft 71. This is accomplished, in the illustrated mechanism, by sensing rotational movement of motor stator 75 that is caused directly by the interruption of rotation of shaft 71 brought about by accumulation of sand above the level of sensing rotor 101. As soon as switch 84 is closed, it completes an energizing circuit to the operating solenoid of control valve 63. Actuation of control valve 63 is in turn effective to actuate operating cylinder 62, driving piston rod 61 downwardly and thereby opening valve 36.

As Valve 36 opens, a discharge is established outwardly of the valve. Sensing rotor 101 is positioned in the path of the resultant downward flow of sand and water. The downwardly moving material, as it engages helical blades 193 and 104, drives the rotor, rotating it in the direction of arrow A. That is, the configuration of the sensing rotor is such that, in response to an outward discharge through valve 36, it applies a restoring torque to shaft 71 that is in aiding relation to the torque applied to the shaft by motor 73. The combined effect of the motor torque and the restoring torque supplied by sensing rotor 191 causes rotor 191 to resume rotation and also rotates the complete drive motor, including stator 75, back toward its initial position. Indeed, motor 73 may be rotated back beyond the initial position shown in solid lines in the drawings, the limit of counterclockwise rotation (FIG. 3) being established by engagement of the stop element 91 with the fixed support member 7 8.

It will be appreciated that the establishrnntof a restoring torque due to the effect of outflowing material on sensing rotor 151 is not dependent upon a discharge sulficient to reduce the sand to a level below the sensing rotor. Rather, the restoring torque is created almost as soon as valve 36 opens, since the only time delay is the time necessary to initiate a substantial flow of material outwardly of the discharge valve. Consequently, the sensing rotor 101 may cause the motor 73 to return to its initial position, with resultant opening of control switch 84, before sand level is reduced below the sensing rotor.

' When this occurs, and there is still enough sand adjacent sensing rotor 1111 to interrupt rotation, the rotor is again stopped by the sand, causing motor stator 75 again to rotate in a clockwise direction and thereby actuate control switch 84 to closed condition. Closing of switch 84 again opens valve 36, again establishing a flow of material downwardly over sensing rotor 191. As before, rotor 1111 applies a restoring torque to shaft 71 to rotate the drive motor back to its original position and open switch 84, causing the discharge valve to be closed.

In control device 46, there are no restoring springs or similar mechanism establishing a normal or home position for the sensing and control apparatus. Consequently, the calibration problems associated with restoration devices of this kind are not presented, and device 46 alfords substantially improved sensitivity as the result of elimination of the conventional restoring springs. The effective restoration of the outlet valve to closed condition is achieved by utilizing the flow of sand and water from the tank to afford a positive restoring torque, closing the valve a short time after it has been opened regardless of the quantity of sand that has been discharged. The resultant intermittent operation of the discharge valve, whenever sand is present above the level of sensing rotor 101, makes it possible to achieve a more even distribution of material discharged from valve 36 in the total material discharged from the scalping tank. At the same time, device 46 still prevents opening of the discharge valve in the absence of substantial accumulation of settled sand or other material 57.

In device 46, as shown in FIG. 2, sensing rotor 101 performs a dual function. That is, the sensing rotor operates to interrupt rotational movement of shaft 71 and thus provides a positive indication of accumulation of sand above the level of the rotor. The rotor also operates as a propeller to apply a restoring torque to the shaft as soon as valve 36 is opened to a substantial extent and a downward flow of water and sand is established around the sensing rotor. It is not essential, however, that both functions be performed by a single rotary element. For example, if it were desired to open valve 36 in response to accumulation of a very small quantity of sand at the bottom of tank 1i shaft 71 may be extended beyond rotor 101, with a small sensing paddle member mounted at the lower lever. Where this construction is employed, interruption of shaft movement is effected by the sensing paddle but the restoring torque for closing the valve is still obtained from rotor 101. In most applications, however, the most effective and economical apparatus entails but a single sensing rotor such as described above and illustrated in the drawings.

Hence, while preferred embodiments of the invention have been described and illustrated, it is to be understood that they are capable of variation and modification, and I therefore do not wish to be limited to the precise details set forth, but desire to avail myself of such changes and alterations as fall within the purview of the following claims.

I claim:

1. A sensing and control device for controlling the discharge of settlings from a water scalping tank or like apparatus in which material is settled out of a fluid medium, and including a discharge valve, said device comprising:

a sensing rotor shaft extending into said fluid in said tank;

drive means for rotating said shaft in a given direction, said drive means applying a predetermined drive torque to said shaft;

sensing rotor means, mounted on said shaft at a predetermined level relative to said discharge valve, for applying a reaction torque to said shaft, opposed to said drive torque, suflicient to interrupt rotation of said shaft whenever settled material exceeds said level, said sensing rotor means having a configuration such that it applies a restoring torque to said shaft, in aiding relation to said drive torque, in response to an outward discharge through said valve;

and control means for sensing interruption in rotation of said shaft and for actuating said discharge valve in response thereto.

2. A sensing and control device for controlling the discharge of settlings from a water scalping tank or like apparatus in which material is settled out of a fluid medium, and including a discharge valve, said device comprising:

a sensing rotor shaft extending into said fluid in said tank;

drive means for rotating said shaft in a given direction, said drive means applying a predetermined drive torque to said shaft;

a sensing rotor, mounted on said shaft at a predetermined level above said discharge valve and in proximity thereto, for applying a reaction torque to said shaft, opposed to said drive torque, sufiicient to interrupt rotation of said shaft whenever settled material exceeds said level, said sensing rotor having at least one blade element of propeller-like configuration such that said rotor applies a restoring torque to said shaft, in aiding relation to said drive torque, in response to an outward discharge through said valve;

and control means for sensing interruption in rotation of said shaft and for actuating said discharge valve to open condition in response thereto.

3. A sensing and control device for controlling the discharge of settlings from a water scalping tank or like apparatus in which material is settled out of a fluid medium, and including a discharge valve, said device comprising:

a sensing rotor shaft extending into said fluid in said tank;

a drive motor connected to said shaft for rotating said shaft in a given direction, said drive motor applying a predetermined drive torque to said shaft;

a helical-blade sensing rotor, mounted on said shaft at a predetermined level above said discharge valve in position to apply a reaction torque to said shaft, opposed to said drive torque, suflicient to interrupt rotation of said shaft whenever settled material exceeds said level, said sensing rotor having a configuration such that it applies a restoring torque to said shaft, in aiding relation to said drive torque, in response to an outward flow of fluid through said discharge valve;

and control means for sensing interruptions in rotation of said shaft and for actuating said discharge valve in response thereto.

4. A sensing and control device for controlling the discharge of settlings from a water scalping tank or like apparatus in which material is settled out of a fluid medium, and including a discharge valve, said device comprising:

a sensing rotor shaft extending downwardly into said fluid in said tank;

drive means, comprising a motor mounted on the upper end of said shaft, for rotating said shaft in a given direction, said drive means applying a predetermined drive torque to said shaft;

suspension means for suspending said motor and shaft in operative position and permitting rotational movement of said motor within a predetermined range;

a sensing rotor, mounted on said shaft at a predetermined level relative to said discharge valve in position to apply a reaction torque to said shaft, opposed to said drive torque, sufficient to interrupt rotation of said shaft and to rotate said motor to one end of said range whenever settled material exceeds said level, said sensing rotor having a configuration such that it applies a restoring torque to said shaft, in aiding relation to said drive torque, in response to an outward discharge through said valve, to rotate said motor to the other end of said range;

and control means for sensing interruption in rotation of said shaft and for actuating said discharge valve in response thereto.

5. A sensing and control device for controlling the discharge of settlings from a water scalping tank or like apparatus in which material is settled out of a fluid medium, and including a discharge valve, said device comprising:

a drive motor, including a stator and an output shaft, and having a predetermined output torque, mounted for axial rotation of said stator within a predetermined range;

a rotor shaft connected to the shaft of said motor and projecting into the fluid in said tank near the discharge valve;

sensing means, mounted on said shaft at a given level above the discharge valve, for applying a reaction torque to said shaft sufficient to interrupt shaft rotation and rotate said motor stator to one end of said range whenever settled material exceeds said level; means responsive to opening of said discharge valve for applying a restoring torque to said shaft to rotate the motor stator back to the other end of said range;

and control means for actuating said discharge valve to open condition in response to rotation of said motor stator to said one end of said range.

6. A sensing and control device for controlling the discharge of settlings from a water scalping tank or like apparatus in which material is settled out of a fluid medium, and including a discharge valve, said device comprising:

a drive motor, including a stator and an output shaft having a predetermined output torque, said stator being mounted for axial rotation within a predetermined range;

a rotor shaft connected to the shaft of said motor and projecting into the fluid in said tank near the discharge valve;

sensing means, mounted on said shaft at a given level and control means, including a sensing switch connected to said motor stator, for actuating said discharge valve to open condition in response to rotation of said motor stator to said one end of said range and for restoring said discharge valve to closed condition in response to rotation of said motor stator to the other end of said range.

and projecting into the fluid in said tank near the discharge valve;

a sensing rotor, mounted on said shaft at a given level above the discharge valve, for applying a reaction torque to said shaft sufficient to interrupt shaft rotation and to cause said motor stator to rotate in a given direction whenever settled material exceeds said level, said sensing rotor including at least one propeller blade for applying a restoring torque to said shaft to rotate the motor stator in the opposite direction in response to a discharge through said valve;

and control means for opening said discharge valve in response to rotation of said motor stator in said one direction, said control means comprising a pivotally actuatable electrical switch mechanically connected to said motor stator.

References Cited in the file of this patent UNITED STATES PATENTS 7. A sensing and control device for controlling the dis- 20 n 1,265,734 Brnnker May 14, 1918 charge 01 settlings from a water scalping tann or like ap- 1 686 435 Chance Oct 2 1928 paratus in which material is settled out of a fluid medium, 2321514 Reed June 1943 and including a discharge valve, said device comprising: 2:325:925 Waugh Aug 3 1943 a drive motor, including a stator and an armature; 25 3,029,374 Pichon 10, 1962 means for suspending said stator at the top of said tank for axial rotation within a predetermined range; FOREIGN PATENTS a rotor shaft connected to the armature of said motor 591,654 Germany I an. 25, 1934 

1. A SENSING AND CONTROL DEVICE FOR CONTROLLING THE DISCHARGE OF SETTLINGS FROM A WATER SCALPING TANK OR LIKE APPARATUS IN WHICH MATERIAL IS SETTLED OUT OF A FLUID MEDIUM, AND INCLUDING A DISCHARGE VALVE, SAID DEVICE COMPRISING: A SENSING ROTOR SHAFT EXTENDING INTO SAID FLUID IN SAID TANK; DRIVE MEANS FOR ROTATING SAID SHAFT IN A GIVEN DIRECTION, SAID DRIVE MEANS APPLYING A PREDETERMINED DRIVE TORQUE TO SAID SHAFT; SENSING ROTOR MEANS, MOUNTED ON SAID SHAFT AT A PREDETERMINED LEVEL RELATIVE TO SAID DISCHARGE VALVE, FOR APPLYING A REACTION TORQUE TO SAID SHAFT, OPPOSED TO SAID DRIVE TORQUE, SUFFICIENT TO INTERRUPT ROTATION OF SAID SHAFT WHENEVER SETTLED MATERIAL EXCEEDS SAID LEVEL, SAID SENSING ROTOR MEANS HAVING A CONFIGURATION SUCH THAT IT APPLIES A RESTORING TORQUE TO SAID SHAFT, IN AIDING RELATION TO SAID DRIVE TORQUE, IN RESPONSE TO AN OUTWARD DISCHARGE THROUGH SAID VALVE; AND CONTROL MEANS FOR SENSING INTERRUPTION IN ROTATION OF SAID SHAFT AND FOR ACTUATING SAID DISCHARGE VALVE IN RESPONSE THERETO. 